Overview

This interface layer handles the communication with Etcd via the etcd-proxy interface.

Usage

Requires

This interface layer will set the following states, as appropriate:

• {relation_name}.connected The relation is established, but Etcd may not yet have provided any connection or service information.

• {relation_name}.available Etcd has provided its cluster string information, and is ready to handle incoming connections. The provided information can be accessed via the following methods:

  • cluster_string()

• {relation_name}.tls.available Etcd has provided client connection credentials for TLS communication.

  • client_ca - CA certificate
  • client_cert - Client Cert
  • client_key - Client Key

For example, a common application for this is configuring an applications backend kv storage, like Docker.

@when('proxy.available')defprepare_etcd_proxy(proxy):
con_string=proxy.cluster_string()
# Save certificates to diskproxy.save_client_credentials('/etc/ssl/etcd')
opts= {}
opts['cluster_string'] =con_stringopts['client_ca'] ='/etc/ssl/etcd/client-ca.pem'opts['client_cert'] ='/etc/ssl/etcd/client-cert.pem'opts['client_key'] ='/etc/ssl/etcd/client-key.pem'render('proxy_systemd_template', '/etc/systemd/system/etcd-proxy.service', opts)

Provides

A charm providing this interface is providing the Etcd cluster management connection string. This is similar to what ETCD requires when peering, declared as:

etcd0=https://192.168.1.2:2380,etcd1=https://192.168.2.22:2380

This interface layer will set the following states, as appropriate:

• {relation_name}.connected One or more clients of any type have been related. The charm should call the following methods to provide the appropriate information to the clients:

  • {relation_name}.provide_cluster_string()

• Additionally to secure the Etcd network connections, All of the client certificate keys must be set, which is conveniently enabled as a method on the interface:

Example:

@when('proxy.connected')defsend_cluster_details(proxy):
bag=EtcdDatabag()
# Read the client credentialsca=read_file_contents('/etc/ssl/etcd/ca.pem')
cert=read_file_contents('/etc/ssl/etcd/client-cert.pem')
key=read_file_contents('/etc/ssl/etcd/client-key.pem')
# Set the cluster string for bootstrapproxy.set_cluster_string(bag.cluster_string())
# Set the client credentialsproxy.set_client_credentials(key, cert, ca)
defread_file_contents(filepath):
withopen(filepath, 'r') asfp:
returnfp.read(filepath)

Contact Information

Maintainer

• Charles Butler <charles.butler@canonical.com>

Contributors

• Mathew Bruzek <mathew.bruzek@canonical.com>

Etcd

• Etcd home page
• Etcd bug trackers
• Etcd Juju Charm